1. Field of the Invention
The present invention relates to an amplifier for use in a radio-frequency band.
2. Description of the Related Art
High gain and high output power are essential features of amplifiers to be used in GHz bands, and for output amplifiers in particular, and it is of extreme importance to provide output matching in the bands used. Inadequate output matching can cause unnecessary reflection from external circuits such as an antenna, with the occurrence of abnormal circuit oscillation and the like. Output amplifiers to be used in an ultra-wideband communication system such as UWB must provide output matching across the entire band.
Radio-frequency transmitters typically have a band-pass filter in the prior stage of an antenna so as to eliminate harmonics other than the carrier frequency. In order for such a band-pass filter to have favorable pass band characteristics, its circuit constants must be set accurately with respect to the application-required center frequency and bandwidth.